Panel drive circuits (semiconductor integrated circuits) of display panels such as liquid crystal panels and organic EL (electroluminescent) panels, generally include a gamma correction circuit for setting gamma characteristics (gamma values) in accordance with the characteristics of each individual display panel. Also, there are panel drive circuits that include an unevenness correction circuit for correcting luminance unevenness and color unevenness that occur at a hardware level, by superimposing reverse phase data of the unevenness on the original image for each region or each pixel of the display panel.
With a panel drive circuit that is provided with a gamma correction circuit and an unevenness correction circuit, in the case where the unevenness correction circuit is upstream of (processes input from outside before) the gamma correction circuit, the luminance characteristics of the display panel with respect to the output of the unevenness correction circuit are known (generally, parameters are determined such that the gamma correction circuit is adjusted to a predetermined gamma characteristic before implementing an unevenness correction, and individual differences between products are minimized) as the product specification of a panel module that combines the panel drive circuit (particularly the gamma correction circuit) and the display panel, thus enabling the unevenness correction in the unevenness correction circuit to be performed utilizing these luminance characteristics. For example, because a derivative (dL/dV) indicating the change in luminance (dL) to the change in input digital value (dV) is determined, if the luminance characteristics of the panel with respect to input are curve characteristics in which γ (gamma value)=2.2, as the product specification of the panel module, the unevenness correction circuit need only perform the unevenness correction, using correction data calculated based on the derivative.
In the case of wanting to obtain display with a gamma characteristic other than the gamma characteristic (gamma value) set previously, such as in the case of wanting to change the gamma characteristic in order to obtain display that is easy to see outdoors where it is bright, for example, the settings of the gamma correction circuit have to be changed. There is, however, a problem in that it becomes necessary, at this time, to perform the unevenness correction after generating correction data adjusted to the changed gamma characteristic, complicating the algorithm for the unevenness correction.
In contrast, as described in Patent Document 1, in the case where a color unevenness correction execution unit (unevenness correction circuit) is downstream of (processes input from outside after) a gamma correction execution unit (gamma correction circuit), the gamma characteristics of a circuit block downstream of the unevenness correction circuit that are targeted for correction by the unevenness correction circuit do not change, even if the settings of the gamma correction circuit are changed, thus enabling the unevenness correction to be performed using the same algorithm as before the settings of the gamma correction circuit are changed.